The Medjugorje phenomenon is one angle to approach this question.

Medjugorje is a false Marian apparition not approved by the Church. According to Catholic historian and Medjugorje expert E. Michael Jones,

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the massacre of Surmanci…took place just on the other side of the [Medjugorje] apparition hill

and

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There were also numerous links between the Medjugorje branch of the Franciscans and the Ustashe.

Thus, condemning Medjugorje would seem to imply condemning the Ustashe.

The Feb. 1998 issue of of Culture Wars ran a section of E. Michael Jones's 2010 The Medjugorje Deception (on Amazon) called "The Ghosts of Surmanci: Queen of Peace, Ethnic Cleansing, Ruined Lives" in which Jones wrote:

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The Franciscan-orchestrated attacks on the Bishop of Mostar are one indication that some things never change in this story. A drive through Medjugorje indicates the exact opposite. Perhaps the best way of resolving the conflict is to say that the more things change, the more they remain the same. The Catholic Church did end up condemning Medjugorje in 1991, but St. James Church continued to attract pilgrims. Even the war didn’t stop that completely. The statement of condemnation issued by the Yugoslavian Bishops’ Conference in Zadar in April 1991 was similarly fraught with ambivalence. It stated that there was nothing supernatural about the occurrences at Medjugorje, but then went on to add that the pilgrims should be taken care of, which prompted the Franciscans to claim that Medjugorje had been officially recognized as a shrine for pilgrims without specifying just why anyone should go there since officially nothing supernatural had ever happened there. Pilgrims to what, one is tempted to ask. Eventually, Rome stepped in and said, in effect, no, Medjugorje had not been recognized as a shrine.

Jones also mentions Cardinal Stepinac in that article. See also Jones's YouTube interview "" (subtitled in Croatian), in which he discusses the Ustashe.

Also, Medjugorje contains doctrine against Catholicism. For example, Fr. Luigi Villa's Chiesa viva 454 November 2012 article "Medjugorje: A Fake Charismatism" (pp. 4-5) reports this heresy in the apparition:

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Serious writers point out that the faith proposed by the “Virgin” of Medjugorje is pluralistic, not in accordance with Catholic dogma: “... for God all the religions are the same: In God, there are no divisions or religions. You in the world have created divisions”

Francis condemned Medjugorje on 13 May 2017:

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Pope Francis: ... The apparitions, the presumed current apparitions: the report [Ruini] has its doubts. I personally am more nasty, I prefer the Madonna as Mother, our Mother, and not a woman who’s the head of a telegraphic office, who everyday sends a message at such hour. This is not the Mother of Jesus. And these presumed apparitions don’t have a lot of value. This I say as a personal opinion. But, it’s clear. Who thinks that the Madonna says, ‘come tomorrow at this time, and at such time I will say a message to that seer?’ No.